Bubble-type electrolytic level sensors of the single-axis and two-axis type are presently in widespread use in guidance systems, missile launch systems, stable platforms, machine tool levelling systems, and the like. Such level sensors use a fluid as an electrolyte to detect variations from level about one or two axis, depending upon the type used. When connected in an appropriate bridge circuit excited by an AC voltage, the sensor output is a voltage whose magnitude is proportional to tilt angle, and whose phase (0.degree. - 180.degree.) indicates the direction of tilt.
In many navigational systems, such as in the case of heading reference systems, it is usual to multiply the output of a bubble level sensor by a second term, such as azimuth rate (AZ). This multiplication is formed in the prior art systems by a separate electronic multiplier which requires additional equipment and circuitry, and substantial expense if precise results are required. The electronic multiplier circuits require expert attention, since they must be calibrated and trimmed for proper operation.
In the system of the present invention, however, the multiplication is performed in the bubble level sensor itself, thus obviating the need for the separate and additional electronic multiplier. The resulting system of the invention is less complex and less expensive than the prior art systems, and it also eliminates errors inherent in the electronic multiplier, and it also obviates the need for trimming or calibration of the multiplier.